Gardaí probing the murder of Kenneth O'Brien have recovered all parts of the power saw used to dismember his body after he was shot dead.

The discovery is considered a major breakthrough by investigating gardaí as the prime suspect in the case remains in custody today.

Mr O'Brien, a father of one from west Dublin, was shot in the head and his remains were dismembered using equipment before being disposed at various locations.

His torso was discovered in mid-January in the Grand Canal at Ardclough, in Lexlip.

A father and son were arrested last Saturday in connection with the murder and yesterday the son, aged in his 30s, was released after five days of questioning.

After the two arrests, gardaí sealed off a house in Finglas and a forensic examination of the building was not completed until yesterday.

Gardaí now believe they have recovered all of the power saw used after the murder.

A motorised component of the power tool was retrieved from the Royal Canal, at Carton, Maynooth, in north Kildare last month and blades were located earlier this week in a pond at Lumville on the Curragh after a search.

Further searches took place this week as dozens of gardaí combed a landfill in Co Wicklow in an attempt to find the murder weapon and missing pieces of the victim's head.

The prime suspect is known to gardaí and has been under investigation in the past for suspected links to an organised crime gang, as well as a connection to the Continuity IRA.

Both men came to light as persons of interest more than a week ago and were placed under garda surveillance prior to their arrest.

Meanwhile, two investigating officers have also travelled to Australia in a bid to find out more about Mr O'Brien's life there. He had lived in Australia for three years before returning to the capital.

Originally from Ballyfermot, Mr O'Brien lived in Clondalkin with his partner and their young child.

Mr O'Brien left his home at Lealand Road in Clondalkin at 7am on Friday, January 15, after telling his partner that he was travelling for work. Gardaí believe he met his killer by arrangement.

One line of inquiry being pursued at the moment is that Mr O'Brien's death was at the hands of a criminal gang following a dispute over money.